A traditional direct current step-down converting circuit which employs resistors connected in series has same load current (output current) and input current. The conversion efficiency of this converting circuit is usually less than 50% (the conversion efficiency is equal to the ratio of an output voltage×output current (Vout.Iout) to an input voltage×input current (Vin.Iin)). In some cases the conversion efficiency is as low as 30%. Moreover, a large amount of heat is produced due to extremely high loss rate of electric energy, therefore a heat sink or cooling system is usually configured for heat dissipation.
Therefore, an improvement solution is desired.